PSI - Issue 78

Luca Rota et al. / Procedia Structural Integrity 78 (2026) 671–677

676

Frequency Domain Decomposition (FDD)

Stochastic Subspace Identification (SSI)

Frequency

Mode shape

Frequency

Mode shape

[Hz] 4.14 4.44 7.17 10.03 15.11 17.86 18.94 19.50 21.53 22.22 23.39 26.33 27.47 28.94 31.69 34.97

[-]

[Hz] 4.14 4.44 7.17 9.92 14.87 18.01 19.28 21.71 22.20 23.23 23.82 26.39 27.49 28.58 30.55 34.77

[-]

Hybrid Hybrid Hybrid Hybrid Hybrid Hybrid Vertical Vertical Vertical Vertical Hybrid Vertical Vertical Hybrid Hybrid Hybrid

Transverse

Hybrid Hybrid Hybrid Hybrid Vertical Vertical Vertical Hybrid Vertical Vertical Hybrid Hybrid Hybrid

Transverse

Transverse

Table 1. Summary of identified modal parameters.

Conclusions A system identification study of a full-scale masonry vault was presented, resulting in the identification of sixteen mode shapes using Frequency Domain Decomposition (FDD) and Stochastic Subspace Identification (SSI-Cov). The identified modes included transverse, vertical and hybrid modes. Both algorithms provided largely consistent results, although some discrepancies were noted, such as modes occurring at slightly different frequencies or identified by only one method. These discrepancies may be due to measurement noise or to the complex dynamic behaviour of the vault. The acceleration data was collected before any damage occurred. Although the investigation is still ongoing, the results already show an extremely complex structural behaviour, which underlines the need for further research. The dynamic behaviour appears to be strongly influenced by several interacting factors, including boundary conditions, geometric configuration and material properties. This complexity underlines the importance of complementary tools such as finite element modelling to achieve an accurate and comprehensive dynamic characterisation. The identified modal parameters provide a valuable benchmark for future assessments and serve as a critical reference for evaluating the evolution of the vault in case of damage. The research will now continue with post-damage experimental investigations aimed at tracking the changes in modal properties. These upcoming analyses will play a key role in calibrating the increasingly refined numerical models and in developing compatible, sustainable strengthening strategies. Ultimately, deepening our understanding of the seismic response of masonry cross vaults is not only a complex engineering task, but also a fundamental step towards the preservation of architectural and cultural heritage. Acknowledgements This study was carried out within the “Structural Rehabilitation of Vaults in Heritage As -set Learning: collapse identification and design of compatible strengthening systems supported by adaptive 3D models - REVHEAL” project – funded by European Union – Next Generation EU within the PRIN 2022 PNRR program (D.D.1409 del 14/09/2022 Ministero dell’Università e della Ricerca). This manuscript reflects only the authors’ views and opinions and the Ministry cannot be considered responsible for them.